DE102020204677B4 - Tracking system and computer program for compensating for visual shadows when tracking measuring objects - Google Patents

Abstract

Tracking system (110) comprising at least one tracking unit (114) which is set up to track a movement of at least one measurement object (112) relative to the tracking unit (114), the tracking system (110) comprising at least one secondary system (116), the secondary system (116) is set up to determine at least one piece of information about a position and/or orientation of the measurement object (112) in space in at least one visual shadow (118) of the tracking unit (114), the visual shadow (118) of the tracking unit (114) is an area of a measurement volume of the tracking unit (114) which cannot be observed and/or seen by the tracking unit (114), the visual shadow (118) being generated by interrupting a line of sight between the measurement object (112) and the tracking unit (114). , wherein the tracking system (110) comprises at least one data processing unit (120), wherein the data processing unit (120) is set up to at least one data gap caused by the visual shadow (118) in the tracking of the measurement object (112) taking into account the data from the secondary system ( 116) to compensate for information determined about the position and/or orientation of the measurement object (112), wherein the compensation involves interpolating and/or extrapolating data recorded by the tracking unit (114), taking into account the information determined by the secondary system (116) about the Position and/or orientation of the measurement object (112), the tracking unit (114) being set up to determine a pose of the measurement object (112) at a plurality of support points (140), the tracking unit (114) being set up to determine a pose of the measurement object (112) at an entry point (136) and an exit point (138) of the visual shadow (118), wherein the data processing unit (120) is set up to calculate at least one tracking trajectory (T) from the poses at the to determine the respective reference point (140), the secondary system (116) being set up to determine the information about the position and/or orientation of the measurement object (112) at a plurality of secondary reference points (142), the secondary system (116) is set up to determine the information about the position and/or orientation of the measurement object (112) at the entry point (136) and at the exit point (138), the data processing unit (120) being set up to take at least one secondary trajectory S into account of the secondary interpolation points (142), the data processing unit (120) being set up to adapt the secondary trajectory S to the tracking trajectory (T).

Description

technical field

The invention relates to a tracking system and a computer program for automatically compensating for visual shadows when tracking at least one measurement object. The present invention relates in particular to the field of coordinate measuring technology using optical coordinate measuring devices.

Technical background

Various methods and devices for tracking measurement objects, also referred to as tracking, are known from the prior art, in particular with the aid of optical trackers. With optical tracking, there must be a permanent line of sight between the optical tracking unit and the measurement object in order to be able to determine its pose, i.e. position and orientation, in the measurement volume. This applies equally to a wide variety of tracking technologies. If there is no line of sight, data gaps can arise.

The line of sight between the tracker and the measurement object can be interrupted, for example, by the measurement object obscuring itself, by carrier kinematics or the user, or by other interference contours such as a clamping device. Depending on the measurement task, the precondition of the visibility of a measurement object can limit the accessibility and flexibility of the system.

U.S. 2006/0221072 A1 describes a system for creating photorealistic 3D models of environments and/or objects from a variety of stereo images obtained by a mobile stereo camera and optional monocular cameras. The system automatically detects and tracks features in image sequences and self-references the stereo camera in 6 degrees of freedom, matching the features to a database to track camera movement while simultaneously building the database. Individual stereo pairs are processed to compute dense 3D data representing the scene and are transformed to a common reference using the estimated camera motion and fused together. The resulting 3D data is represented as point clouds, surfaces or volumes. Systems and methods for the three-dimensional view of the environment are US2014/0043436A1 , U.S. 2013/0004060 A1 and US 2014/0176677 A1 described.

object of the invention

It would therefore be desirable to provide a tracking system and a computer-implemented method for compensating for data gaps which at least largely avoid the disadvantages of known devices and methods. In particular, a simplified handling of tracking systems in the interactive as well as in the automated application should be made possible.

General Description of the Invention

This object is addressed by a tracking system and a computer program having the features of the independent patent claims. Advantageous developments, which can be implemented individually or in any combination, are presented in the dependent claims.

In the following, the terms "have", "have", "comprise" or "include" or any grammatical deviations thereof are used in a non-exclusive manner. Accordingly, these terms can refer both to situations in which, apart from the features introduced by these terms, no further features are present, or to situations in which one or more further features are present. For example, the expression "A has B", "A has B", "A comprises B", or "A includes B" can both refer to the situation in which, apart from B, there is no other element in A (i.e. to a situation in which A consists exclusively of B), as well as to the situation in which, in addition to B, there are one or more other elements in A, e.g. element C, elements C and D or even other elements .

Furthermore, it is pointed out that the terms "at least one" and "one or more" as well as grammatical variations of these terms, if they are used in connection with one or more elements or features and are intended to express that the element or feature is provided once or several times can generally only be used once, for example when the feature or element is introduced for the first time. If the feature or element is subsequently mentioned again, the corresponding term “at least one” or “one or more” is usually no longer used, without restricting the possibility that the feature or element can be provided once or more than once.

Furthermore, the terms "preferably", "in particular", "for example" or similar terms in connection with optional Features used without alternative embodiments are thereby limited. Thus, features introduced by these terms are optional features and are not intended to limit the scope of the claims, and in particular the independent claims, by these features. Thus, as will be appreciated by those skilled in the art, the invention may be practiced using other configurations. Similarly, features introduced by "in an embodiment of the invention" or by "in an exemplary embodiment of the invention" are understood as optional features without intending to limit alternative configurations or the scope of the independent claims. Furthermore, through these introductory expressions, all possibilities to combine the features introduced here with other features, be they optional or non-optional features, remain untouched.

In a first aspect, a tracking system is proposed within the scope of the present invention. The term "system" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term may refer, without limitation, to a device comprising a plurality of components or elements that cooperate at least in part to perform at least one function. The term "tracking system" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term may refer, without limitation, to a device for tracking at least one measurement object.

The term "measurement object" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, refer in particular to an arbitrarily shaped object to be measured. For example, the measurement object can be selected from the group consisting of a test piece, a workpiece, a component to be measured, and a measuring head of a sensor. The measurement object can have at least one marker and/or retroreflector.

The tracking system includes at least one tracking unit that is set up to track a movement of at least one measurement object relative to the tracking unit. The tracking system includes at least one secondary system. The secondary system is set up to determine at least one piece of information about a position of the measurement object in space in at least one visual shadow of the tracking unit. The tracking system includes at least one data processing unit. The data processing unit is set up to compensate for at least one data gap caused by the visual shadow when tracking the measurement object, taking into account the information about the position of the measurement object determined by the secondary system. Compensating includes interpolating and/or extrapolating data recorded by the tracking unit, taking into account the information about the position and/or orientation of the measurement object determined by the secondary system.

The term "tracking entity" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, refer in particular to an optical device that is set up to track a movement of the measurement object relative to the tracking unit. The tracking unit can include at least one optical measuring system. The tracking unit can be set up to measure distance, also referred to as depth measurement, and/or to determine pose. The optical measurement system can have at least one system selected from the group consisting of: at least one laser tracker; at least one triangulation system comprising at least three line scan cameras; at least one triangulation system based on the stereo vision method, comprising at least two area cameras; at least one multilateration system, for example at least one trilateration system comprising at least three LiDAR channels; at least one monocular area camera. The term "laser tracker" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, refer in particular to any measuring device which is set up to interferometrically determine a distance and/or a direction of a retroreflector, in particular relative to axes which are defined by an optomechanics of the laser tracker. The laser tracker can, for example, be in the form of a Leica AT-960 laser tracker. A "triangulation system" can basically be understood as any optical measuring system, which is set up to determine a distance between the measurement object and the tracking unit based on a triangulation method. The term "line scan camera" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to a camera which has a light-sensitive line, in particular a line sensor. For example, the line cameras can each have a plurality of pixels which are arranged in a line. The line cameras can have CCD sensors or CMOS sensors, for example. The line scan cameras can be designed, for example, as T-TRACK from ZEISS. In principle, a “stereo vision method” can be understood to mean any method for three-dimensional vision using at least two cameras. The term "area scan camera" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term can refer, without limitation, to a camera that includes at least one sensor that has a matrix with a plurality of rows and/or columns of pixels. For example, the area scan cameras can be designed as AICell Trace from ZEISS. A “trilateration system” can in principle be understood to mean any optical measuring system that is set up to determine a distance between the measurement object and the tracking unit based on a trilateration method. In the context of the present invention, a "LiDAR channel" can basically be understood as a measurement channel of a LiDAR sensor, with the LiDAR sensor being based on the LiDAR ("light detection and ranging") measurement principle, also known as LaDAR (laser detection and ranging). called, based. In particular, the LiDAR sensor can be set up to generate and receive a light beam, for example a laser beam, in particular the light beam previously emitted by it and reflected back to it, and from this to determine a distance between the LiDAR sensor and the measurement object, for example exploiting differences in return times and wavelengths. Alternatively or additionally, the tracking unit can have at least one monocular area camera, for example from OptiNav.

The term "relative movement" of the measurement object to the tracking unit, as used herein, is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to a movement of the measurement object and/or the tracking unit. For example, the measurement object can be arranged on a measurement table, the measurement table being set up to move the measurement object during the measurement operation. In this example, the tracking unit can have a fixed position in space. Alternatively or additionally, the tracking unit can be moved. The measurement object and/or the tracking unit can move in a common inertial system and relative to one another, but independently of one another.

The term "tracking" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, refer in particular to determining a position of the measurement object at at least two different times.

The term “measurement object position” as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, refer in particular to three translational degrees of freedom. The term "orientation of the target" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, refer in particular to three rotational degrees of freedom. The translational and rotational degrees of freedom can also be referred to as a pose, which define a total of 6 degrees of freedom. The position can be a three-dimensional point (X, Y, Z) in the coordinate system, in particular a position of the measurement object. The spatial position can be defined by the location coordinates X, Y and Z. The position can include a distance, also referred to as distance, between a point on a surface of the measurement object and the tracking unit. The distance can be a longitudinal coordinate of the measurement object. An “orientation” can be understood as meaning a position in space, in particular a rotation, of the measurement object, in particular an angular position. The orientation can be specified by at least three angles, for example Euler angles or pitch angles, roll angles and yaw angles. The determination of Distance and orientation can be referred to as pose determination.

The term "visual shadow" of the tracking unit, as used herein, is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to an area of a measurement volume of the tracking unit which cannot be observed and/or viewed by the tracking unit. The visual shadow is created by interrupting a line of sight between the measurement object and the tracking unit. Line of sight disruption can be caused by at least one occlusion. The occlusion can include self-occlusion, for example by the measurement object, or by external occlusion, for example by carrier kinematics or a user or by other interfering contours such as a clamping device. In the visual shadow, it may be impossible for the tracking unit to determine distance and/or pose. The tracking unit cannot determine any poses in the visual shadow between the entry point and the exit point.

The term "entry point" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to a first spatial boundary, in particular a spatial beginning, of the visual shadow. The tracking unit can be set up to determine the pose of the measurement object in the measurement volume in front of the visual shadow up to and including the entry point. The term "exit point", also called end point of the view shadow, as used herein, is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, refer in particular to a second limit different from the first limit, in particular a spatial end, of the visual shadow. The tracking unit can be set up to determine the pose of the measurement object after the visual shadow, including the exit point.

The term "secondary system" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to an additional data source which is set up to generate and/or provide at least one piece of information about a position and/or orientation of the measurement object in space in the visual shadow of the tracking unit. The tracking system can have a plurality of secondary systems, it being possible for the secondary systems to be configured identically or differently. The secondary system can have at least one sensor, in particular at least one position-giving system. The secondary system can have at least one position-giving system selected from the group consisting of: at least one position sensor, in particular at least one gyroscope; at least one inertial sensor in or on the measurement object to be tracked; at least one axis encoder of a carrier kinematics; at least one area camera; at least one absolute measuring system. The secondary system can, for example, include a measuring head that references itself using marks on or next to the component, such as a HandyScan from Creaform® or a K-SCAN20 from SCANTECH. The area camera can be arranged, for example, in a measuring head of the coordinate measuring machine and determine the information about the position using SLAM (“Simultaneous Localization and Mapping”) algorithms. For example, the secondary system can be an absolutely measuring system, which is constructed in the same way as the tracking unit, but which is not necessarily calibrated to the tracking unit, ie measures in a different local coordinate system. The secondary system can alternatively or additionally be a data source which provides predictions about a pose of the measurement object, for example an a priori data source. The a priori data source can be a database, for example, in which a corresponding secondary trajectory is stored for a set of known poses before and after the data gap. The database can be filled (“trained”), for example, by random selection of sections of selected lengths in example trajectories that are otherwise known without gaps. The selection of the most suitable data set can be done with pertinent machine learning methods or by using metrics that evaluate the similarity of poses or sets of poses in terms of position and/or orientation. The information about the pose of the measurement object can include a distance of the measurement object from the secondary system and/or an orientation of the measurement object. As explained above, the tracking unit cannot determine any poses in the visual shadow between the entry point and the exit point. Instead, the secondary system can be configured to collect information in the view shadow. Those from the secondary system The information generated can have sufficient relative accuracy so that missing poses can be interpolated and, in particular, error propagation can be minimized.

The term "data processing unit" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term may refer specifically, without limitation, to any logic circuitry for performing basic operations of a computer or system, and/or generally to any device configured to perform calculations or logical operations. The data processing unit can have a processor or a processor unit. The data processing unit may include, for example, an arithmetic logic unit (ALU), a floating point unit (FPU) such as a math coprocessor or numeric coprocessor, a plurality of registers, and a work memory, for example a cache work memory. The data processing unit can have a multi-core processor. The data processing unit can have a central processing unit (CPU). Alternatively or additionally, the data processing unit can have one or more application-specific integrated circuits and/or one or more Field Programmable Gate Arrays (FPGAs) or the like.

The term "data gap" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. Specifically, the term may refer, without limitation, to at least one missing datum and/or at least one missing section in a record. The data record can describe a relative movement of the measurement object, in particular a plurality of poses. The data gap may relate to poses not captured and therefore missing from the dataset during relative movement. The data gap may be caused by a break in tracking the measurement object. The interruption can be caused by the tracking unit's visual shadow, in particular as a result of an interference contour.

The term "compensating" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term may refer, without limitation, to filling a data gap and/or completing the data set.

Compensation includes interpolation, also referred to as interpolation, and/or extrapolation, also referred to as extrapolation, taking into account the information about the position and/or orientation of the measurement object determined by the secondary system. The interpolation can determine poses between poses known by the tracking unit, i.e. poses determined with the tracking unit at reference points before the entry point, the pose determined with the tracking unit at the entry point, poses determined with the tracking unit at reference points after the exit point and he with the tracking unit specific pose at the exit point. The interpolation can basically include using any interpolation method. Interpolating can include linear, quadratic, or cubic interpolation. For example, for the translational component, the linear interpolation can include determining at least one unknown point between two known points, assuming that the unknown point is on a straight line connecting the known points. With linear interpolation, the course of a curve between two known points can be assumed to be a first-order polynomial. Other linear interpolations are also conceivable. For example, a linear interpolation can take place without a geometric reference to a straight line. For example, calculations can be made in polar coordinates instead of in Cartesian coordinates. The quadratic interpolation may include determining at least one unknown point between two known points, assuming a quadratic curve progression between two known points. The shape of the curve between the two known points can be assumed to be a second-order polynomial. The cubic interpolation includes determining at least one unknown point between two known points, assuming a cubic curve progression between two known points. The shape of the curve between the two known points can be assumed to be a third-order polynomial. The compensation can also include an extrapolation. The extrapolation can include determining a behavior of the trajectory beyond a range that can be detected with the tracking unit. During the interpolation, a parameter a can run from 0 to 1 between the two support points. During the extrapolation, this range of values can be extended upwards and/or downwards. An extrapolation can be used in particular if there are support points on only one side. An interpolation can be used if there are reference points on both sides gen. A trajectory of the measurement object can be completely determined following the compensation.

The term "trajectory" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term may refer, without limitation, to a path and/or trajectory that describes the relative movement of the measurement object. The trajectory can be described as a mathematical function, also called a curve. The trajectory can be linear, for example. The trajectory can also run in any curve shape. In particular, the trajectory can be a continuous function.

The term "support point" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term can refer, without limitation, to a spatial coordinate used to determine the trajectory. The pose of the measurement object at the reference point can also be referred to as the reference value. The tracking unit is set up to determine a pose of the measurement object at a plurality of support points, also referred to as primary support points. The tracking unit is set up to determine the pose of the measurement object at the entry point and the exit point of the visual shadow. The data processing unit is set up to determine at least one tracking trajectory from the pose at the respective support point. The term "tracking trajectory", also referred to as primary trajectory, as used herein, is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to a trajectory which takes into account interpolation points at which the pose of the measurement object was determined by the tracking unit. The tracking unit can be set up to determine a plurality of interpolation points before the entry point and after the exit point of the visual shadow.

The secondary system is set up to determine the information about the position and/or orientation of the measurement object at a plurality of secondary interpolation points. The secondary system is set up to determine the information about the position and/or orientation of the measurement object at the entry point and at the exit point. The secondary system can be set up to determine the information about the position and/or orientation of the measurement object between the entry point and the exit point. The data processing unit is set up to determine at least one secondary trajectory S, taking into account the secondary interpolation points. The term "secondary support point" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term may refer, without limitation, to a spatial coordinate used to determine the secondary trajectory. The term "secondary trajectory" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, relate in particular to a trajectory that takes into account support points at which the information about the position and/or orientation of the measurement object was determined by the secondary system. The secondary support points can lie at least partially within the tracking unit's line of sight.

Due to interruptions during the measurement of the measurement object by the tracking unit, the actual trajectory of the measurement object can sometimes no longer be directly traceable as a result of visual shadows. Instead, one or more secondary systems can collect information that is used to interpolate and/or extrapolate the tracking trajectory. A presumed trajectory, the secondary trajectory, can thus be determined. Due to the error propagation in secondary systems with systems that measure relatively or systems that measure absolutely with less accuracy, a suspected trajectory can deviate locally and/or globally from the actual trajectory and/or deviate from it. A C ₀ point of discontinuity can thus arise after an exit from and potentially also when entering the visual shadow. At the C ₀ point of discontinuity, the trajectory cannot simply be continuously differentiable. The data processing unit is set up to adapt the secondary trajectory S to the tracking trajectory. The term "customize" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term can refer, without limitation, to a modification of the secondary trajectory. Adjusting the secondary trajectory can take place in such a way that at the entry and/or exit points there is at least C ₀ continuity, preferably C ₁ continuity, and particularly preferably C ₂ continuity. The secondary trajectory can be adapted in such a way that the error propagation is minimal, so that both trajectories coincide as well as possible. Both requirements can relate both to the location and to the orientation of the measurement object.

und $$D_1=A\cdot S{\left(1\right)}^{-1}$$

sein. Die Differenztransformationen können Transformationen der bogenlängenparametrisierten Sekundärtrajektorie am Eintritts- und Austrittspunkt in Transformationen der Trackingtrajektorie überführen. Das Anpassen der Sekundärtrajektorie S(x) = S_T(x) · S_R(x) an die Trackingtrajektorie kann durch eine lineare Interpolation erfolgen, beispielsweise mit: $$S_T\left(x\right):=x\cdot D_{\mathrm{1,}T}\cdot S_T\left(x\right)+\left(1-x\right)\cdot D_{\mathrm{0,}T}\cdot S_T\left(x\right),$$

$$S_R\left(x\right):=x\cdot D_{\mathrm{1,}R}\cdot S_R\left(x\right)+\left(1-x\right)\cdot D_{\mathrm{0,}R}\cdot S_R\left(x\right),$$

wobei sich S_T(x) und S_R(x) translatorische und rotatorische Anteile der Sekundärtrajektorie, D_1,T ein translatorischer Anteil der Differenztransformation D₁, D_1,R ein rotatorischer Anteil der Differenztransformation D₁, D_0,T ein translatorischer der Differenztransformation D₀, und D_0,R ein rotatorischer Anteil der Differenztransformation D₀ ist.The tracking trajectory and the secondary trajectory can describe a sequence of affine transformations over their respective arc lengths. In particular, the tracking trajectory and the secondary trajectory can describe a sequence of Euclidean transformations; in particular, no shearing is considered and therefore angular fidelity is also required. The object to be measured, or the measuring head, can be viewed as a rigid body. The term "arc length" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term may refer specifically, without limitation, to a geometrical length of a curve. The term "affine transformation" as used herein is a broad term which should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term may refer, without limitation, to a structure-preserving mapping that preserves collinearity, parallelism, and part ratios. The affine transformation can include translations and/or rotations. The affine transformations can be broken down into their translational and rotational parts. The translational part can be described with vector algebra. The rotational part can be described with quaternion algebra. However, other forms of notation are also conceivable. In the following, for reasons of readability, matrix notation is used for executing transformations one after the other. The transformations from the coordinate system of the tracking unit at the entry point and the exit point can be denoted by E and A. The secondary trajectory S can be parameterized according to the parameter x arc length: S(x): 0 ≤ x ≤ 1. S(x=0), or S(0) for short, can refer to the secondary trajectory at the entry point. S(x=1), or S(1) for short, may refer to the secondary trajectory at the exit point. Difference transformations D of the tracking trajectory and the secondary trajectory can accordingly $${\mathrm{<figure-callout\; id="0"\; label="D"\; filenames="DE102020204677B4\_0014.png"\; state="\{\{state\}\}">D</figure-callout>}}_0=E\cdot S{\left(0\right)}^{-1}$$

and $${\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="DE102020204677B4\_0014.png"\; state="\{\{state\}\}">D</figure-callout>}}_1=A\cdot S{\left(1\right)}^{-1}$$

be. The difference transformations can convert transformations of the arc length parameterized secondary trajectory at the entry and exit points into transformations of the tracking trajectory. The secondary trajectory S(x) = S _T (x) · S _R (x) can be adapted to the tracking trajectory by linear interpolation, for example with: $$S_T\left(x\right):=x\cdot D_{\mathrm{1,}T}\cdot S_T\left(x\right)+\left(1-x\right)\cdot D_{\mathrm{0,}T}\cdot S_T\left(x\right),$$

$$S_R\left(x\right):=x\cdot D_{\mathrm{1,}R}\cdot S_R\left(x\right)+\left(1-x\right)\cdot D_{\mathrm{0,}R}\cdot S_R\left(x\right),$$

where S _T (x) and S _R (x) translational and rotational components of the secondary trajectory, D _1,T a translational component of the differential transformation D ₁ , D _1,R a rotational component of the differential transformation D ₁ , D _0,T a translatory of the differential transformation D ₀ , and D _0,R is a rotational component of the differential transformation D ₀ .

Adjusting the translational part of the secondary trajectory can lead to C ₀ continuity at S(0) and S(1). The adaptation of the rotary part can lead to a C ₀ continuity at S(0) and S(1). Higher-order continuity can be achieved by means of quadratic or cubic instead of linear interpolations of the translational and rotational components of the associated transformations. In order to achieve C1 continuity, for example, at least one quadratic interpolation and correspondingly more support points at the edges of the visual shadow can be considered.

The tracking system can include at least one controller. The controller can be set up to control at least one component of the tracking unit. The controller can also be set up to control at least one component of the secondary system. In particular, the controller can be set up to control at least one component of the secondary system in such a way that the secondary system tracks the measurement object at least in the visual shadow of the tracking unit. The controller can include at least one data processing device, for example at least one computer or at least one microcontroller. The data processing device can have one or more volatile and/or non-volatile data memories, it being possible for the data processing device to be set up in terms of programming, for example, to control the tracking unit and the secondary system. The controller can also include at least one interface, for example an electronic interface and/or a man-machine interface such as for example an input/output device such as a display and/or a keyboard. For example, one or more electronic connections can be provided between the tracking unit and the controller and the secondary system and the controller. The controller can, for example, have a centralized or decentralized structure. Other configurations are also conceivable.

A further aspect of the present invention proposes a computer program or a computer-implemented method for automatically compensating for at least one data gap when tracking at least one measurement object.

The term "computer-implemented," as used herein, is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. In particular, the term may refer, without limitation, to a method involving at least one computer and/or at least one computer network. The computer and/or the computer network can comprise at least one processor, the processor being set up to carry out at least one method step of the computer-implemented method of the invention. Each of the method steps is preferably carried out by the computer and/or the computer network.

The method can be carried out automatically and in particular without user interaction. The term "automatic" as used herein is a broad term that should be given its ordinary and current meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can, without limitation, refer in particular to a process that is performed entirely by a computer and/or a computer network and/or a machine, in particular without user interaction and/or manual intervention. User interaction may be required to initiate the process and/or individual process steps. The user interaction may include selecting at least one record and/or entering at least one command.

In the method, a tracking system according to the invention is used in one of its configurations. For definitions and configurations of the method, reference can be made to definitions and configurations of the tracking system.

1. a. Nachverfolgen einer Bewegung des Messobjektes relativ zu mindestens einer Trackingeinheit;
2. b. Bestimmen und/oder Bereitstellen mindestens einer Information über eine Position und/oder Orientierung des Messobjekts im Raum in mindestens einem Sichtschatten der Trackingeinheit mit mindestens einem Sekundärsystem;
3. c. Kompensieren mindestens einer durch den Sichtschatten entstandenen Datenlücke bei der Nachverfolgung des Messobjekts unter Berücksichtigung der von dem Sekundärsystem bestimmten Information über die Position und/oder Orientierung des Messobjekts mit mindestens einer Datenverarbeitungseinheit, wobei das Kompensieren ein Interpolieren und/oder Extrapolieren von durch die Trackingeinheit aufgenommenen Daten unter Berücksichtigung der von dem Sekundärsystem bestimmten Information über die Position und/oder Orientierung des Messobjekts umfasst.

The computer-implemented method for automatically compensating for at least one data gap when measuring at least one measurement object comprises the following steps, which, as an example, can be carried out in the following order. It is also possible to carry out one or more of the process steps once or several times in a repetitive manner. The method can also include further method steps that are not listed. Furthermore, it is possible to carry out two or more of the method steps simultaneously or at least with a time overlap.

1. a. tracking a movement of the measurement object relative to at least one tracking unit;
2. b. determining and/or providing at least one piece of information about a position and/or orientation of the measurement object in space in at least one visual shadow of the tracking unit with at least one secondary system;
3. c. Compensating for at least one data gap caused by the visual shadow when tracking the measurement object, taking into account the information determined by the secondary system about the position and/or orientation of the measurement object with at least one data processing unit, the compensation involving an interpolation and/or extrapolation of data recorded by the tracking unit taking into account the information determined by the secondary system about the position and/or orientation of the measurement object.

Furthermore, within the scope of the present invention, a computer program is proposed which, when run on a computer or computer network, executes the method according to the present description in one of its configurations.

Furthermore, within the scope of the present invention, a computer program with program code means is proposed in order to carry out the method, according to the present description, in one of its configurations when the program is run on a computer or computer network. In particular, the program code means can be stored on a computer-readable data carrier and/or a computer-readable storage medium.

The terms "computer-readable data medium" and "computer-readable storage medium" as used herein can refer in particular to non-transitory data storage, for example a hardware data storage medium, on which computer-executable instructions are stored are saved. The computer-readable data carrier or the computer-readable storage medium can in particular be or include a storage medium such as a random access memory (RAM) and/or a read-only memory (ROM).

In addition, the present invention proposes a data carrier on which a data structure is stored which, after loading into a working and/or main memory of a computer or computer network, can be used to carry out the method according to the present description in one of its configurations.

The present invention also proposes a computer program product with program code means stored on a machine-readable carrier in order to carry out the method according to the present description in one of its configurations when the program is run on a computer or computer network.

A computer program product is understood as the program as a tradable product. In principle, it can be in any form, for example on paper or on a computer-readable data medium, and can be distributed in particular via a data transmission network.

Finally, a modulated data signal is proposed which contains instructions executable by a computer system or computer network for carrying out a method according to the present description. With regard to the computer-implemented aspects of the invention, one, several or even all method steps of the method according to one or more of the configurations proposed here can be carried out by means of a computer or computer network. Thus, in general, any of the method steps including the provision and/or manipulation of data can be performed using a computer or computer network. In general, these steps may include any of the method steps, excluding steps that require manual work, such as user input of commands.

The proposed devices and methods have numerous advantages over known devices and methods. Poses can also be determined with a high degree of accuracy when the tracking unit is not supplying any data. Secondary system accuracy requirements can be low. It does not have to be absolutely measuring, nor true to size. The error propagation can be limited to half the arc length of the suspected trajectory. If the system properties are known and largely constant, it can be calculated relatively precisely a priori under which conditions the location and/or orientation accuracy is still below a specified error limit, for example a length and duration of the occlusion.

• Ausführungsform 1: Trackingsystem umfassend mindestens eine Trackingeinheit, welche eingerichtet ist, eine Bewegung mindestens eines Messobjekts relativ zu der Trackingeinheit nachzuverfolgen, wobei das Trackingsystem mindestens ein Sekundärsystem umfasst, wobei das Sekundärsystem eingerichtet ist, um mindestens eine Information über eine Position und/oder Orientierung des Messobjekts im Raum in mindestens einem Sichtschatten der Trackingeinheit zu bestimmen, wobei das Trackingsystem mindestens eine Datenverarbeitungseinheit umfasst, wobei die Datenverarbeitungseinheit eingerichtet ist, um mindestens eine durch den Sichtschatten entstandene Datenlücke bei der Nachverfolgung des Messobjekts unter Berücksichtigung der von dem Sekundärsystem bestimmten Information über die Position und/oder Orientierung des Messobjekts zu kompensieren, wobei das Kompensieren ein Interpolieren und/oder Extrapolieren von durch die Trackingeinheit aufgenommenen Daten unter Berücksichtigung der von dem Sekundärsystem bestimmten Information über die Position und/oder Orientierung des Messobjekts umfasst.
• Ausführungsform 2: Trackingsystem nach der vorhergehenden Ausführungsform, wobei die Trackingeinheit mindestens ein optisches Messsystem aufweist, ausgewählt aus der Gruppe bestehend aus: mindestens einem Lasertracker; mindestens einem Triangulationssystem umfassend mindestens drei Zeilenkameras; mindestens einem Multilaterationssystem, beispielsweise mindestens einem Triangulationssystem nach dem Stereo-Vision-Verfahren umfassend mindestens zwei Flächenkameras; mindestens einem Trilaterationssystem umfassend mindestens drei LiDAR-Kanäle; mindestens einer monokularen Flächenkamera.
• Ausführungsform 3: Trackingsystem nach einer der vorhergehenden Ausführungsformen, wobei das Sekundärsystem mindestens ein positionsgebendes System aufweist, ausgewählt aus der Gruppe bestehend aus: mindestens einem Lagesensor; mindestens einem Inertialsensor im oder am nachzuverfolgenden Messobjekt; mindestens einem Achs-Encoder einer Trägerkinematik; mindestens einer Flächenkamera; mindestens einem absolut messenden System.
• Ausführungsform 4: Trackingsystem nach einer der vorhergehenden Ausführungsformen, wobei die Trackingeinheit eingerichtet ist, um an einer Mehrzahl von Stützstellen jeweils eine Pose des Messobjekts zu bestimmen, wobei die Trackingeinheit eingerichtet ist, um an einem Eintrittspunkt und einem Austrittspunkt des Sichtschattens jeweils eine Pose des Messobjekts zu bestimmen, wobei die Datenverarbeitungseinheit eingerichtet ist, um mindestens eine Trackingtrajektorie aus den Posen an der jeweiligen Stützstelle zu bestimmen.
• Ausführungsform 5: Trackingsystem nach der vorhergehenden Ausführungsform, wobei die Trackingeinheit eingerichtet ist, um an einer Mehrzahl von Stützstellen vor dem Eintrittspunkt und nach dem Austrittspunkt des Sichtschattens jeweils eine Pose des Messobjekts zu bestimmen.
• Ausführungsform 6: Trackingsystem nach einer der zwei vorhergehenden Ausführungsformen, wobei das Sekundärsystem eingerichtet ist, um an einer Mehrzahl von Sekundärstützstellen jeweils die Information über die Position und/oder Orientierung des Messobjekts zu bestimmen, wobei das Sekundärsystem eingerichtet ist, um an dem Eintrittspunkt, zwischen dem Eintrittspunkt und dem Austrittspunkt und an dem Austrittspunkt die Information über die Position und/oder Orientierung des Messobjekts zu bestimmen, wobei die Datenverarbeitungseinheit eingerichtet ist, um mindestens eine Sekundärtrajektorie S unter Berücksichtigung der Sekundärstützstellen zu bestimmen.
• Ausführungsform 7: Trackingsystem nach der vorhergehenden Ausführungsform, wobei die Datenverarbeitungseinheit eingerichtet ist, um die Sekundärtrajektorie S an die Trackingtrajektorie anzupassen.
• Ausführungsform 8: Trackingsystem nach der vorhergehenden Ausführungsform, wobei die Sekundärtrajektorie S nach einem Parameter x bogenlängenparametrisiert ist: S(x): 0 ≤ x ≤ 1, wobei die das Anpassen der Sekundärtrajektorie S(x) = S_T(x) · S_R(x) an die Trackingtrajektorie durch eine lineare Interpolation erfolgt mit: $$S_T\left(x\right):=x\cdot D_{\mathrm{1,}T}\cdot S_T\left(x\right)+\left(1-x\right)\cdot D_{\mathrm{0,}T}\cdot S_T\left(x\right),$$
  
  $$S_R\left(x\right):=x\cdot D_{\mathrm{1,}R}\cdot S_R\left(x\right)+\left(1-x\right)\cdot D_{\mathrm{0,}R}\cdot S_R\left(x\right),$$
  
  wobei S_T(x) und S_R(x) translatorische und rotatorische Anteile der Sekundärtrajektorie ist, wobei D_1,T ein translatorischer Anteil einer Differenztransformation D₁ = A · S(1)^-1 ist, mit einer Transformation des Austrittspunkt A aus einem Koordinatensystem der Trackingeinheit, und D_1,R ein rotatorischer Anteil der Differenztransformation D₁ ist, wobei D_0,T ein translatorischer einer Differenztransformation D₀ = E · S(0)^-1 ist, mit einer Transformation des Eintrittspunktes E aus dem Koordinatensystem der Trackingeinheit und D_0,R ein rotatorischer Anteil der Differenztransformation D₀ ist.
• Ausführungsform 9: Trackingsystem nach einer der vorhergehenden Ausführungsformen, wobei das Trackingsystem mindestens eine Steuerung umfasst, welche dazu eingerichtet ist, mindestens eine Komponente der Trackingeinheit anzusteuern, wobei die Steuerung eingerichtet ist mindestens eine Komponente des Sekundärsystems anzusteuern.
• Ausführungsform 10: Computerimplementiertes Verfahren zur automatischen Kompensation von mindestens einer Datenlücke bei einer Nachverfolgung mindestens eines Messobjekts, wobei in dem Verfahren ein Trackingsystem nach einer der vorhergehenden, ein Trackingsystem betreffenden Ausführungsformen verwendet wird, wobei das Verfahren folgende Schritte umfasst:
  1. a. Nachverfolgen einer Bewegung des Messobjektes relativ zu mindestens einer Trackingeinheit;
  2. b. Bestimmen und/oder Bereitstellen mindestens einer Information über eine Position und/oder Orientierung des Messobjekts im Raum in mindestens einem Sichtschatten der Trackingeinheit mit mindestens einem Sekundärsystem;
  3. c. Kompensieren mindestens einer durch den Sichtschatten entstandenen Datenlücke bei der Nachverfolgung des Messobjekts unter Berücksichtigung der von dem Sekundärsystem bestimmten Information über die Position und/oder Orientierung des Messobjekts mit mindestens einer Datenverarbeitungseinheit, wobei das Kompensieren ein Interpolieren und/oder Extrapolieren von durch die Trackingeinheit aufgenommenen Daten unter Berücksichtigung der von dem Sekundärsystem bestimmten Information über die Position und/oder Orientierung des Messobjekts umfasst.
• Ausführungsform 11: Computerprogramm, welches bei Ablauf auf einem Computer oder Computernetzwerk ein Verfahren zur automatischen Kompensation von Datenlücken nach einer der vorhergehenden, ein Verfahren betreffenden Ausführungsformen, insbesondere die Verfahrensschritte a. bis c., in einer seiner Ausgestaltungen ausführt.
• Ausführungsform 12: Computerprogramm-Produkt mit auf einem maschinenlesbaren Träger gespeicherten Programmcode-Mitteln, um ein Verfahren zur automatischen Kompensation von Datenlücken nach einer der vorhergehenden, ein Verfahren betreffenden Ausführungsformen, in einer seiner Ausgestaltungen, durchzuführen, wenn das Programm auf einem Computer oder Computer-Netzwerk ausgeführt wird.

In summary, the following embodiments are proposed without restricting further possible configurations:

• Embodiment 1: Tracking system comprising at least one tracking unit which is set up to track a movement of at least one measurement object relative to the tracking unit, the tracking system comprising at least one secondary system, the secondary system being set up to record at least one piece of information about a position and/or orientation of the to determine the measurement object in space in at least one visual shadow of the tracking unit, the tracking system comprising at least one data processing unit, the data processing unit being set up to detect at least one data gap caused by the visual shadow when tracking the measurement object, taking into account the information about the position determined by the secondary system and/or to compensate for the orientation of the measurement object, wherein the compensation comprises an interpolation and/or extrapolation of data recorded by the tracking unit, taking into account the information about the position and/or orientation of the measurement object determined by the secondary system.
• Embodiment 2 Tracking system according to the preceding embodiment, wherein the tracking unit has at least one optical measuring system selected from the group consisting of: at least one laser tracker; at least one triangulation system comprising at least three line scan cameras; at least one multilateration system, for example at least one triangulation system using the stereo vision method, comprising at least two area cameras; at least one trilateration system comprising at least three LiDAR channels; at least one monocular area camera.
• Embodiment 3: tracking system according to one of the preceding embodiments, wherein the secondary system has at least one position-giving system selected from the group consisting of: at least one position sensor; at least one inertial sensor in or on the measurement object to be tracked; at least one axis encoder of a carrier kinematics; at least one area camera; at least one absolute measuring system.
• Embodiment 4: Tracking system according to one of the preceding embodiments, wherein the tracking unit is set up to determine a pose of the measurement object at a plurality of support points, the tracking unit being set up to determine a pose of the measurement object at an entry point and an exit point of the visual shadow to determine, wherein the data processing unit is set up to determine at least one tracking trajectory from the poses at the respective support point.
• Embodiment 5 tracking system according to the previous embodiment, wherein the tracking unit is set up to determine a pose of the measurement object at a plurality of interpolation points before the entry point and after the exit point of the visual shadow.
• Embodiment 6: Tracking system according to one of the two preceding embodiments, wherein the secondary system is set up to determine the information about the position and/or orientation of the measurement object at a plurality of secondary reference points, the secondary system being set up to, at the entry point, between to determine the entry point and the exit point and at the exit point the information about the position and/or orientation of the measurement object, the data processing unit being set up to determine at least one secondary trajectory S taking into account the secondary interpolation points.
• Embodiment 7 tracking system according to the previous embodiment, wherein the data processing unit is set up to adapt the secondary trajectory S to the tracking trajectory.
• Embodiment 8: Tracking system according to the previous embodiment, wherein the secondary trajectory S is arc length parameterized according to a parameter x: S(x): 0 ≤ x ≤ 1, wherein the adaptation of the secondary trajectory S(x) = S _T (x) S _R (x) to the tracking trajectory by a linear interpolation is done with: $$S_T\left(x\right):=x\cdot D_{\mathrm{1,}T}\cdot S_T\left(x\right)+\left(1-x\right)\cdot D_{\mathrm{0,}T}\cdot S_T\left(x\right),$$
  
  $$S_R\left(x\right):=x\cdot D_{\mathrm{1,}R}\cdot S_R\left(x\right)+\left(1-x\right)\cdot D_{\mathrm{0,}R}\cdot S_R\left(x\right),$$
  
  where S _T (x) and S _R (x) are translational and rotational parts of the secondary trajectory, where D _1,T is a translational part of a difference transformation D ₁ = A · S(1) ^-1 , with a transformation of the exit point A from a coordinate system of the tracking unit, and D _1,R is a rotational part of the difference transformation D ₁ , where D _0,T is a translational part of a difference transformation D ₀ = E · S(0) ^-1 , with a transformation of the entry point E from the coordinate system of the tracking unit and D _0,R is a rotational component of the differential transformation D ₀ .
• Embodiment 9 tracking system according to one of the preceding embodiments, wherein the tracking system comprises at least one controller which is set up to control at least one component of the tracking unit, the controller being set up to control at least one component of the secondary system.
• Embodiment 10: Computer-implemented method for automatically compensating for at least one data gap when tracking at least one measurement object, wherein a tracking system according to one of the preceding embodiments relating to a tracking system is used in the method, the method comprising the following steps:
  1. a. tracking a movement of the measurement object relative to at least one tracking unit;
  2. b. determining and/or providing at least one piece of information about a position and/or orientation of the measurement object in space in at least one visual shadow of the tracking unit with at least one secondary system;
  3. c. Compensating for at least one data gap caused by the visual shadow when tracking the measurement object, taking into account the information determined by the secondary system about the position and/or orientation of the measurement object with at least one data processing unit, the compensation involving an interpolation and/or extrapolation of data recorded by the tracking unit taking into account the information determined by the secondary system about the position and/or orientation of the measurement object.
• Embodiment 11: Computer program which, when running on a computer or computer network, implements a method for automatically compensating for data gaps according to one of the preceding embodiments relating to a method, in particular method steps a. to c., in one of its configurations.
• Embodiment 12 Computer program product on a machine-readable carrier stored program code means to carry out a method for the automatic compensation of data gaps according to one of the preceding embodiments relating to a method, in one of its refinements, when the program is executed on a computer or computer network.

character list

Further details and features emerge from the following description of exemplary embodiments, in particular in connection with the dependent claims. The respective features can be implemented individually or in combination with one another. The invention is not limited to the exemplary embodiments. The exemplary embodiments are shown schematically in the figures. The same reference numerals in the individual figures designate elements that are the same or have the same function or that correspond to one another in terms of their functions.

• 1 ein Ausführungsbeispiel für ein erfindungsgemäßes Trackingsystem;
• 2 eine schematische Darstellung einer Unterbrechung der Sichtverbindung bei einer Nachverfolgung eines Messobjekts mit einer Trackingeinheit;
• 3 ein Ausführungsbeispiel einer Anpassung der Sekundärtrajektorie S an die Trackingtrajektorie; und
• 4 ein Flussdiagramm eines Ausführungsbeispiels des Verfahrens.

Show in detail:

• 1 an embodiment of a tracking system according to the invention;
• 2 a schematic representation of an interruption of the line of sight when tracking a measurement object with a tracking unit;
• 3 an exemplary embodiment of an adaptation of the secondary trajectory S to the tracking trajectory; and
• 4 a flowchart of an embodiment of the method.

Description of the exemplary embodiments

1 12 shows an exemplary embodiment of a tracking system 110 according to the invention. The tracking system 110 can include at least one device for tracking at least one measurement object 112. Tracking system 110 may include a plurality of components or elements that cooperate at least in part to perform at least one function. The measurement object 112 can include an arbitrarily shaped object to be measured. For example, the measurement object 112 can be selected from the group consisting of a test piece, a workpiece, a component to be measured, and a measuring head of a sensor. The measurement object 112 can have at least one marker and/or retroreflector.

The tracking system 110 includes at least one tracking unit 114, which is set up to track a movement of at least one measurement object 112 relative to the tracking unit 114. Tracking system 110 includes at least one secondary system 116. Secondary system 116 is set up to determine at least one piece of information about a position and/or orientation of measurement object 112 in space in at least one visual shadow 118 of tracking unit 114. Tracking system 110 includes at least one data processing unit 120. Data processing unit 120 is set up to close at least one data gap caused by visual shadow 118 when tracking measurement object 112, taking into account the information determined by secondary system 116 about the position and/or orientation of measurement object 112 compensate. Compensation includes interpolating and/or extrapolating data recorded by tracking unit 114, taking into account the information about the position and/or orientation of measurement object 112 determined by secondary system 116.

The tracking unit 114 can include an optical device which is set up to track a movement of the measurement object 112 relative to the tracking unit 114 . The tracking unit 114 can include at least one optical measuring system. Tracking unit 114 can be set up to measure distance, also referred to as depth measurement, and/or to determine pose. The optical measurement system can have at least one system selected from the group consisting of: at least one laser tracker; at least one triangulation system comprising at least three line scan cameras; at least one triangulation system based on the stereo vision method, comprising at least two area cameras; at least one multilateration system, for example at least one trilateration system comprising at least three LiDAR channels; at least one monocular area camera. The laser tracker can include any measuring device that is set up to determine a distance and/or a direction of a retroreflector interferometrically, in particular relative to axes that are defined by an optomechanics of the laser tracker. The laser tracker can, for example, be in the form of a Leica AT-960 laser tracker. The triangulation system can include any optical measurement system that is set up to determine a distance between measurement object 112 and tracking unit 114 based on a triangulation method. The line camera can include a camera which has a light-sensitive line, in particular a line sensor. For example, the line cameras can each have a plurality of pixels which are arranged in a line. The line cameras can, for example, CCD-Senso ren or have CMOS sensors. The line scan cameras can be designed, for example, as T-TRACK from ZEISS. The stereo vision method can include any spatial vision method using at least two cameras. The area camera can include a camera which includes at least one sensor which has a matrix with a plurality of rows and/or columns of pixels. For example, the area scan cameras can be designed as AICell Trace from ZEISS. The trilateration system can include any optical measuring system that is set up to determine a distance between the measurement object 112 and the tracking unit 114 based on a trilateration method. The LiDAR channel can include a measurement channel of a LiDAR sensor, the LiDAR sensor being based on the LiDAR (light detection and ranging) measurement principle, also called LaDAR (laser detection and ranging). In particular, the LiDAR sensor can be set up to generate and receive a light beam, for example a laser beam, in particular the light beam previously emitted by it and reflected back to it, and from this to determine a distance between the LiDAR sensor and the measurement object 112, for example by exploiting differences in return times and wavelengths. Alternatively or additionally, the tracking unit 114 can have at least one monocular area camera, for example from OptiNav.

A movement of the measurement object 112 relative to the tracking unit 114 can include a movement of the measurement object 112 and/or the tracking unit 114 . For example, the measurement object 112 can be arranged on a measurement table, the measurement table being set up to move the measurement object 112 during the measurement operation. In this example, the tracking unit 114 can have a fixed position in space. Alternatively or additionally, the tracking unit 114 can be moved. In 1 a tracking unit 114 is shown, which is designed as a robot arm and is set up to drive around the measurement object 112 . The movement of the measurement object 112 and/or the tracking unit 114 can take place in a common inertial system and relative to one another, but independently of one another.

The tracking can in particular include determining a position and/or orientation of the measurement object 112 at at least two different times. The position and/or orientation of the measurement object 112 can include a location and/or orientation of the measurement object 112 or a part of the measurement object 112 in space. The position can be a three-dimensional point (X, Y, Z) in the coordinate system 122, in particular a position of the measurement object 112. The spatial position can be defined by the location coordinates X, Y and Z. The position can include a distance, also referred to as a distance, between a point on a surface of the measurement object 112 and the tracking unit 114 . The distance can be a longitudinal coordinate of the measurement object. The orientation can be a position in space, in particular a rotation, of the measurement object 112, in particular an angular position. The orientation can be specified by at least three angles, for example Euler angles or pitch angles, roll angles and yaw angles. The determination of distance and orientation can be referred to as pose determination.

The tracking system 110 includes, among other things, a secondary system 116. The secondary system 116 can, as in 1 shown, be attached directly to the measurement object 112. The secondary system 116 can include an additional data source, which is set up to generate and/or provide at least one piece of information about a position and/or orientation of the measurement object 112 in space in the visual shadow 118 of the tracking unit 114 . The tracking system 110 can have a plurality of secondary systems 116, it being possible for the secondary systems 116 to be configured identically or differently. The secondary system 116 can have at least one sensor, in particular at least one position-giving system. The secondary system 116 can have at least one position-giving system selected from the group consisting of: at least one position sensor, in particular at least one gyroscope; at least one inertial sensor in or on the measurement object 112 to be tracked; at least one axis encoder of a carrier kinematics; at least one area camera; at least one absolute measuring system. The area camera can be arranged, for example, in a measuring head of the coordinate measuring machine and determine the information about the position using SLAM (“Simultaneous Localization and Mapping”) algorithms. For example, the secondary system 116 can be an absolutely measuring system, which has the same construction as the tracking unit 114 , but which is not necessarily calibrated to the tracking unit 114 , ie measures in a different local coordinate system 122 . The secondary system 116 may alternatively or additionally be a data source that provides predictions about a pose of the measurement object, for example an a priori data source. The a priori data source can be a database, for example, in which a corresponding secondary trajectory is stored for a set of known poses before and after the data gap.

The database can be created, for example, by random selection of sections of selected lengths in examples that are otherwise known without gaps rajectories are filled (“trained”). The selection of the most suitable data set can be done with pertinent machine learning methods or by using metrics that evaluate the similarity of poses or sets of poses in terms of position and/or orientation. The information about the position and/or orientation of the measurement object 112 can include a distance of the measurement object 112 from the secondary system 116 and/or an orientation of the measurement object 112 .

The tracking system 110 includes, among other things, a data processing unit 120. The data processing unit 120 can include any logic circuit for performing basic operations of a computer or a system and/or generally a device which is set up for performing calculations or logical operations. The data processing unit 120 can have a processor or a processor unit. The data processing unit 120 may include, for example, an arithmetic logic unit (ALU), a floating point unit (FPU) such as a math coprocessor or numeric coprocessor, a plurality of registers, and a memory, such as a cache memory. The data processing unit 120 can have a multi-core processor. The data processing unit 120 may include a central processing unit (CPU). Alternatively or additionally, the data processing unit 120 may include one or more application specific integrated circuits and/or one or more Field Programmable Gate Arrays (FPGAs) or the like.

The tracking system 110 can further include at least one controller 124 . The controller 124 can be set up to control at least one component of the tracking unit 114 . The controller 124 can also be set up to control at least one component of the secondary system 116 . In particular, the controller 124 can be set up to control at least one component of the secondary system 116 in such a way that the secondary system 116 tracks the measurement object 112 at least in the visual shadow 118 of the tracking unit 114 . The controller 124 can include at least one data processing device 120, for example at least one computer or at least one microcontroller. The data processing device 120 can have one or more volatile and/or non-volatile data memories, wherein the data processing device 120 can be set up in terms of programming, for example, to control the tracking unit 114 and the secondary system 116 . The controller 124 may further include at least one interface 126, such as an electronic interface 126 and/or a human-machine interface 126, such as an input/output device such as a display and/or a keyboard. For example, one or more electronic connections may be provided between the tracking unit 114 and the controller 124 and the secondary system 116 and the controller 124 . The controller 124 can, for example, have a central or decentralized structure. Other configurations are also conceivable.

2 shows a schematic representation of an interruption in the line of sight when tracking a measurement object 112 with a tracking unit 114. An interference contour 128 between measurement object 112 and tracking unit 114 can cause a visual shadow 118 and thereby cover at least part of measurement object 112. As a result, with regard to a trajectory 130 of the measurement object 112 , a difference can arise between an actual trajectory 132 and a trajectory 134 that may be incorrectly assumed as a result of the visual shadow 118 . The visual shadow 118 can include an area of a measurement volume of the tracking unit 114 which cannot be observed and/or viewed by the tracking unit 114 . The visual shadow 118 can be generated or determined by interrupting a line of sight between the measurement object 112 and the tracking unit 114 . Line of sight disruption can be caused by at least one occlusion. The occlusion can include self-occlusion, for example by the measurement object 112, or by an external occlusion, for example by carrier kinematics or a user or by other interfering contours 128 such as a clamping device. In the visual shadow 118, it may be impossible for the tracking unit 114 to determine a distance and/or a pose. The tracking unit 114 cannot determine any poses in the visual shadow 118 between the entry point 136 and the exit point 138 .

The trajectory 130 can in particular include a path and/or a trajectory which describes the relative movement of the measurement object 112 . The trajectory 130 can be described as a mathematical function. The trajectory 130 can run linearly, for example. The trajectory 130 can also run in any curve shape. The trajectory 130 can in particular be a continuous function.

The entry point 136 can include a first spatial boundary, in particular a spatial beginning, of the visual shadow 118 . The tracking unit 114 can be set up to determine the position and/or orientation of the measurement object 112 in the measurement volume in front of the visual shadow 118 to a finally to the entry point 136 to determine. The exit point 138, also called the end point of the visual shadow, can include a second limit, in particular a spatial end, of the visual shadow 118 that is different from the first limit. The tracking unit 114 can be set up to determine the position and/or orientation of the measurement object 112 after the visual shadow 118 including the exit point 138 . In 2 entry point 136 and exit point 138 are indicated by squares.

A data gap that may have arisen as a result of the visual shadow 118 can include at least one missing datum and/or at least one missing section in a data record. The data record can describe a relative movement of the measurement object 112, in particular a plurality of poses. The data gap may relate to poses not captured and therefore missing from the dataset during relative movement. The data gap may be caused by an interruption in the tracking of the device under test 112 . The interruption can be caused by the visual shadow 118 of the tracking unit 114, in particular as a result of an interference contour 128. Compensating for the data gap can in particular include filling the data gap and/or completing the data set.

3 12 shows an exemplary embodiment of an adaptation of the secondary trajectory S to the tracking trajectory T. As explained above, the tracking unit 114 cannot determine any poses in the visual shadow 118 between the entry point 136 and the exit point 138. Instead, the secondary system 116 may be configured to collect information in the view shadow 118 . The information generated by the secondary system 116 can have sufficient relative accuracy so that missing poses can be interpolated and, in particular, error propagation can be minimized.

Compensating for the data gap caused by the visual shadow 118 includes interpolating and/or extrapolating, taking into account the information determined by the secondary system 116 about the position and/or orientation of the measurement object 112. The interpolating can involve determining poses between the tracking unit 114 known poses, i.e. poses determined with tracking unit 114 at support points 142 before entry point 136, the pose determined with tracking unit at entry point 136, poses determined with tracking unit 140 at support points after exit point 138 and the pose determined with tracking unit 114 at the exit point 138, include. The interpolation can basically include using any interpolation method. Interpolating can include linear, quadratic, or cubic interpolation. The linear interpolation may include determining at least one unknown point between two known points, assuming that the unknown point is on a straight line connecting the known points. With linear interpolation, the course of a curve between two known points can be assumed to be a first-order polynomial. Other linear interpolations are also conceivable. For example, a linear interpolation can take place without a geometric reference to a straight line. For example, calculations can be made in polar coordinates instead of in Cartesian coordinates. The quadratic interpolation may include determining at least one unknown point between two known points, assuming a quadratic curve progression between two known points. The shape of the curve between the two known points can be assumed to be a second-order polynomial. The cubic interpolation includes determining at least one unknown point between two known points, assuming a cubic curve progression between two known points. The shape of the curve between the two known points can be assumed to be a third-order polynomial. The compensation can also include an extrapolation. The extrapolation can include determining a behavior of the trajectory 130 beyond a range that can be detected with the tracking unit 114 . During the interpolation, a parameter a can run from 0 to 1 between the two support points. During the extrapolation, this range of values can be extended upwards and/or downwards. An extrapolation can be used in particular if there are support points on only one side. An interpolation can be used if there are reference points on both sides. A trajectory 130 of the measurement object 112 can be completely determined following the compensation.

Support point 140 can in particular include a spatial coordinate that is used to determine trajectory 130 . In 3 the interpolation points 140 are identified by dots. Entry point 136 and exit point 138 are indicated by squares. The tracking unit 114 is set up to determine a pose of the measurement object 112 at a plurality of reference points 140 in each case. The tracking unit 114 is set up to determine the pose of the measurement object 112 at the entry point 136 and the exit point 138 of the visual shadow 118 . The data processing unit 120 is set up to determine at least one tracking trajectory T from the pose at the respective support point 140 . The tracking trajectory T can in particular be a trajectory 130, which takes into account support points 140 at which the pose of the measurement object 112 was determined by the tracking unit 114. The tracking unit 114 can be set up to determine a pose of the measurement object 112 at a plurality of interpolation points 140 in front of the entry point 136 and after the exit point 138 of the visual shadow.

The secondary system 116 is set up to determine the information about the position and/or orientation of the measurement object 112 at a plurality of secondary support points 142 in each case. The secondary system 116 is set up to determine the information about the position and/or orientation of the measurement object 112 at the entry point 136, between the entry point 136 and the exit point 138 and at the exit point 138. The data processing unit 120 is set up to determine at least one secondary trajectory S taking into account the secondary interpolation points 142 .

The secondary reference point 142 can in particular include a spatial coordinate which is used to determine the secondary trajectory S. In 3 secondary support points 142 are identified by crosses. The secondary trajectory S can include, in particular, a trajectory 130 that takes into account support points 140 at which the information about the position and/or orientation of the measurement object 112 was determined by the secondary system 116 . The secondary support points 142 can lie at least partially within the visual shadow 118 of the tracking unit 114 .

Due to interruptions during the measurement of the measurement object 112 by the tracking unit 114, the actual trajectory 130 of the measurement object 112 can sometimes no longer be directly traceable as a result of visual shadows 118. Instead, one or more secondary systems 116 may collect information that is used to interpolate and/or extrapolate the tracking trajectory T. A suspected trajectory 134, the secondary trajectory S, can thus be determined. Due to the error propagation in secondary systems 116 with systems that measure relatively or systems that measure absolutely with less accuracy, a suspected trajectory 134 can deviate locally and/or globally from the actual trajectory 132 and/or deviate from it. After an exit from, and potentially also upon entry into, the visual shadow 118, a C ₀ point of discontinuity can thus arise. At the C ₀ discontinuity, the trajectory 130 cannot simply be continuously differentiable. The data processing unit 120 is set up to adapt the secondary trajectory S to the tracking trajectory T. The adaptation can in particular include a modification of the secondary trajectory S. The secondary trajectory S can be adapted in such a way that at the entry and/or exit points 136 and 138 there is at least C ₀ continuity, preferably C ₁ continuity, and particularly preferably C ₂ continuity. The secondary trajectory S can be adapted in such a way that the error propagation is minimal, so that both trajectories 130 coincide as well as possible. Both requirements can relate both to the location and to the orientation of the measurement object 112 .

und $$D_1=A\cdot S{\left(1\right)}^{-1}$$

sein. Die Differenztransformationen können Transformationen der bogenlängenparametrisierten Sekundärtrajektorie S am Eintritts- und Austrittspunkt 136 bzw. 138 in Transformationen der Trackingtrajektorie überführen. Das Anpassen der Sekundärtrajektorie S(x) = S_T(x) · S_R (x) an die Trackingtrajektorie kann durch eine lineare Interpolation erfolgen, beispielsweise mit: $$S_T\left(x\right):=x\cdot D_{\mathrm{1,}T}\cdot S_T\left(x\right)+\left(1-x\right)\cdot D_{\mathrm{0,}T}\cdot S_T\left(x\right)$$

$$S_R\left(x\right):=x\cdot D_{\mathrm{1,}R}\cdot S_R\left(x\right)+\left(1-x\right)\cdot D_{\mathrm{0,}R}\cdot S_R\left(x\right),$$

wobei sich S_T(x) und S_R(x) translatorische und rotatorische Anteile der Sekundärtrajektorie S, D_1,T ein translatorischer Anteil der Differenztransformation D₁, D_1,R ein rotatorischer Anteil der Differenztransformation D₁, D_0,T ein translatorischer der Differenztransformation D₀, und D_0,R ein rotatorischer Anteil der Differenztransformation D₀ ist. Die Anpassung des translatorischen Anteils der Sekundärtrajektorie S kann zu einer C₀-Stetigkeit bei S(0) und S(1) führen. Die Anpassung des rotatorischen Anteils kann zu einer C0-Stetigkeit bei S(0) und S(1) führen. Stetigkeiten höherer Ordnung können mittels quadratischer oder kubischer statt linearer Interpolationen der translatorischen und der rotatorischen Anteile der zugehörigen Transformationen erreicht werden. 3 verbildlicht, dass durch die Anpassung der Sekundärtrajektorie S ein anfänglicher Unterschied zur tatsächlichen Trajektorie 132 derart aufgehoben werden kann, dass beide im Endergebnis möglichst gut zur Deckung kommen.The tracking trajectory T and secondary trajectory S can describe a sequence of affine transformations over their respective arc lengths. The arc length can in particular include a geometric length of a curve. The affine transformation can include, in particular, a structure-preserving mapping that preserves collinearity, parallelism, and part ratios. The affine transformation can include translations and/or rotations. The affine transformations can be broken down into their translational and rotational parts. The translational part can be described with vector algebra. The rotational part can be described with quaternion algebra. However, other forms of notation are also conceivable. In the following, for reasons of readability, matrix notation is used for executing transformations one after the other. The transformations from the coordinate system 122 of the tracking unit at the entry point 136 and the exit point 138 can be denoted by E and A. The secondary trajectory S can be parameterized according to the parameter x arc length: S(x): 0≦x≦1. S(x=0), or S(0) for short, can refer to the secondary trajectory S at the entry point 136 . S(x=1), or S(1) for short, may refer to the secondary trajectory S at exit point 138 . Difference transformations D of the tracking trajectory and the secondary trajectory S can accordingly $${\mathrm{<figure-callout\; id="0"\; label="D"\; filenames="DE102020204677B4\_0014.png"\; state="\{\{state\}\}">D</figure-callout>}}_0=E\cdot S{\left(0\right)}^{-1}$$

and $${\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="DE102020204677B4\_0014.png"\; state="\{\{state\}\}">D</figure-callout>}}_1=A\cdot S{\left(1\right)}^{-1}$$

be. The difference transformations can convert transformations of the arc length parameterized secondary trajectory S at the entry and exit point 136 or 138 into transformations of the tracking trajectory. The secondary trajectory S(x) = S _T (x) · S _R (x) can be adapted to the tracking trajectory by linear interpolation, for example with: $$S_T\left(x\right):=x\cdot {\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="DE102020204677B4\_0014.png"\; state="\{\{state\}\}">D</figure-callout>}}_{\mathrm{1,}T}\cdot S_T\left(x\right)+\left(1-x\right)\cdot {\mathrm{<figure-callout\; id="0"\; label="D"\; filenames="DE102020204677B4\_0014.png"\; state="\{\{state\}\}">D</figure-callout>}}_{\mathrm{0,}T}\cdot S_T\left(x\right)$$

$$S_R\left(x\right):=x\cdot D_{\mathrm{1,}R}\cdot S_R\left(x\right)+\left(1-x\right)\cdot D_{\mathrm{0,}R}\cdot S_R\left(x\right),$$

where S _T (x) and S _R (x) translational and rotational components of the secondary trajectory S, D _1,T a translational component of the differential transformation D ₁ , D _1,R a rotary component of the differential transformation D ₁ , D _0,T a translatory of the differential transformation D ₀ , and D _0,R is a rotary component of the differential transformation D ₀ . The adaptation of the translational component of the secondary trajectory S can lead to C ₀ continuity at S(0) and S(1). The adaptation of the rotary part can lead to a C0 continuity at S(0) and S(1). Higher-order continuity can be achieved by means of quadratic or cubic instead of linear interpolations of the translational and rotational components of the associated transformations. 3 illustrates that by adapting the secondary trajectory S, an initial difference to the actual trajectory 132 can be eliminated in such a way that both end up congruent as well as possible.

4 shows a flowchart of an exemplary embodiment of the computer-implemented method, according to the present description, for automatically compensating for at least one data gap when tracking at least one measurement object 112. In the method, a tracking system 110 according to the invention is used in one of its configurations. The method may involve at least one computer and/or at least one computer network. The computer and/or the computer network can comprise at least one processor, the processor being set up to carry out at least one method step of the computer-implemented method of the invention. Each of the method steps is preferably carried out by the computer and/or the computer network. The method can be carried out completely automatically and in particular without user interaction.

1. a. Nachverfolgen einer Bewegung des Messobjektes 112 relativ zu mindestens einer Trackingeinheit 114;
2. b. Bestimmen und/oder Bereitstellen mindestens einer Information über eine Position und/oder Orientierung des Messobjekts 112 im Raum in mindestens einem Sichtschatten 118 der Trackingeinheit 114 mit mindestens einem Sekundärsystem 116;
3. c. Kompensieren mindestens einer durch den Sichtschatten 118 entstandenen Datenlücke bei der Nachverfolgung des Messobjekts 112 unter Berücksichtigung der von dem Sekundärsystem 116 bestimmten Information über die Position und/oder Orientierung des Messobjekts 112 mit mindestens einer Datenverarbeitungseinheit 120, wobei das Kompensieren ein Interpolieren und/oder Extrapolieren von durch die Trackingeinheit 114 aufgenommenen Daten unter Berücksichtigung der von dem Sekundärsystem 116 bestimmten Information über die Position und/oder Orientierung des Messobjekts 112 umfasst.

The computer-implemented method for automatically compensating for at least one data gap when measuring at least one measurement object 112 comprises the following steps, which, as an example, can be carried out in the following order. It is also possible to carry out one or more of the process steps once or several times in a repetitive manner. The method can also include further method steps that are not listed. Furthermore, it is possible to carry out two or more of the method steps simultaneously or at least with a time overlap.

1. a. tracking a movement of the measurement object 112 relative to at least one tracking unit 114;
2. b. Determining and/or providing at least one piece of information about a position and/or orientation of the measurement object 112 in space in at least one visual shadow 118 of the tracking unit 114 with at least one secondary system 116;
3. c. Compensating for at least one data gap caused by the visual shadow 118 when tracking the measurement object 112, taking into account the information determined by the secondary system 116 about the position and/or orientation of the measurement object 112 with at least one data processing unit 120, the compensation involving an interpolation and/or extrapolation of includes data recorded by tracking unit 114, taking into account the information determined by secondary system 116 about the position and/or orientation of measurement object 112.

Numeral 144 denotes method step a. Numeral 146 denotes method step b. and reference numeral 148 denotes step c in 4 .

reference list

110

tracking system

112

measurement object

114

tracking unit

116

secondary system

118

visual shade

120

data processing unit

122

coordinate system

124

steering

126

interface

128

interference contour

130

trajectory

132

Actual Trajectory

134

Assumed trajectory

136

entry point

138

exit point

140

base

142

secondary base

144

Process step a.

146

process step b.

148

process step c.

S

secondary trajectory

T

tracking trajectory

Claims (7)

Tracking system (110) comprising at least one tracking unit (114) which is set up to track a movement of at least one measurement object (112) relative to the tracking unit (114), the tracking system (110) comprising at least one secondary system (116), the secondary system (116) is set up to determine at least one piece of information about a position and/or orientation of the measurement object (112) in space in at least one visual shadow (118) of the tracking unit (114), the visual shadow (118) of the tracking unit (114) is an area of a measurement volume of the tracking unit (114) which cannot be observed and/or seen by the tracking unit (114), the visual shadow (118) being generated by interrupting a line of sight between the measurement object (112) and the tracking unit (114). , wherein the tracking system (110) comprises at least one data processing unit (120), wherein the data processing unit (120) is set up to at least one data gap caused by the visual shadow (118) in the tracking of the measurement object (112) taking into account the data from the secondary system ( 116) to compensate for information determined about the position and/or orientation of the measurement object (112), wherein the compensation involves interpolating and/or extrapolating data recorded by the tracking unit (114), taking into account the information determined by the secondary system (116) about the Position and/or orientation of the measurement object (112), the tracking unit (114) being set up to determine a pose of the measurement object (112) at a plurality of support points (140), the tracking unit (114) being set up to determine a pose of the measurement object (112) at an entry point (136) and an exit point (138) of the visual shadow (118), wherein the data processing unit (120) is set up to calculate at least one tracking trajectory (T) from the poses at the to determine the respective reference point (140), the secondary system (116) being set up to determine the information about the position and/or orientation of the measurement object (112) at a plurality of secondary reference points (142), the secondary system (116) is set up to determine the information about the position and/or orientation of the measurement object (112) at the entry point (136) and at the exit point (138), the data processing unit (120) being set up to take at least one secondary trajectory S into account of the secondary interpolation points (142), the data processing unit (120) being set up to adapt the secondary trajectory S to the tracking trajectory (T). Tracking system (110) according to the preceding claim, wherein the tracking unit (114) has at least one optical measuring system selected from the group consisting of: at least one laser tracker; at least one triangulation system comprising at least three line scan cameras; at least one triangulation system based on the stereo vision method, comprising at least two area cameras; at least one multilateration system; at least one monocular area camera. Tracking system (110) according to one of the preceding claims, wherein the secondary system (116) has at least one position-giving system selected from the group consisting of: at least one position sensor; at least one inertial sensor in or on the measurement object (112) to be tracked; at least one axis encoder of a carrier kinematics; at least one area camera; at least one absolute measuring system. Tracking system (110) according to one of the preceding claims, wherein the tracking unit (114) is set up to determine a pose of the visual shadow (118) at a plurality of support points (140) before the entry point (136) and after the exit point (138). To determine the measurement object (112). Tracking system (110) according to one of the preceding claims, wherein the secondary trajectory S is arc length parameterized according to a parameter x: S(x): 0 ≤ x ≤ 1, wherein the adaptation of the secondary trajectory S(x) = S _T (x) S _R (x) to the tracking trajectory (T) by a linear interpolation is done with: $$S_T\left(x\right):=x\cdot D_{\mathrm{1,}T}\cdot S_T\left(x\right)+\left(1-x\right)\cdot D_{\mathrm{0,}T}\cdot S_T\left(x\right),$$

$$S_R\left(x\right):=x\cdot D_{\mathrm{1,}R}\cdot S_R\left(x\right)+\left(1-x\right)\cdot D_{\mathrm{0,}R}\cdot S_R\left(x\right),$$

where S _T (x) and S _R (x) are translational and rotational parts of the secondary trajectory S, where D _1,T is a translational part of a difference transformation D ₁ = A · S(1) ^-1 , with a transformation A of the exit point (138) from a coordinate system (122) of the tracking unit (114), and D _1,R is a rotational component of the differential transformation D ₁ , with D _0,T being a translatory component of a differential transformation D ₀ =E · S(0) ^-1 is, with a transformation E of the entry point (136) from the coordinate system (122) of the tracking unit (114) and D _0,R is a rotary component of the difference transformation D ₀ . Computer program, comprising instructions which, when the computer program is executed by a computer, cause the computer to carry out a method for automatically compensating for at least one data gap when tracking at least one measurement object (112), in which method a tracking system (110) according to one of the preceding , a tracking system (110) related claims is used, and the method at least the following steps a. to c. includes: a. tracking a movement of the measurement object (112) relative to at least one tracking unit (114); b. Determining and/or providing at least one piece of information about a position and/or orientation of the measurement object (112) in space in at least one visual shadow (118) of the tracking unit (114) with at least one secondary system (116), the visual shadow (118) of the tracking unit ( 114) is an area of a measurement volume of the tracking unit (114) which cannot be observed and/or seen by the tracking unit (114), the visual shadow (118) being caused by an interruption of a line of sight between the measurement object (112) and the tracking unit (114) is produced; c. Compensating for at least one data gap caused by the visual shadow (118) when tracking the measurement object (112), taking into account the information determined by the secondary system (116) about the position and/or orientation of the measurement object (112) with at least one data processing unit (120), wherein the compensation comprises an interpolation and/or extrapolation of data recorded by the tracking unit (114), taking into account the information determined by the secondary system (116) about the position and/or orientation of the measurement object (112). Computer program product with program code means stored on a machine-readable carrier, for creating a computer program claim 6 to be performed if the computer program is run on a computer or computer network.

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